The present invention relates to a control device, method and storage medium for an automatic transmission.
There exists a multi-stage automatic transmission mounted on a vehicle or the like. Hydraulic control is performed to engage a plurality of (for example, two) friction engagement elements (clutch or brake) according to a shift speed in order to form a transmission path of a speed change gear mechanism. However, for example, when a hydraulic pressure is output due to a failure (disconnection, or valve sticking, for example) of a linear solenoid valve to a hydraulic servo as a friction engagement element which should be released, there is a possibility that the friction engagement element which should be released is simultaneously engaged in addition to the friction engagement element engaged in a normal state.
Thus, in order to prevent the simultaneous engagement, a configuration has been proposed in which a plurality of so-called cut-off valves which block a hydraulic pressure (source pressure) of an additional friction engagement element when an engagement pressure of friction engagement elements engaged in the normal state is input are provided according to the combination of the friction engagement elements to be engaged in each shift speed to thereby prevent the simultaneous engagement in all shift speeds (for example, see Japanese Patent Application Publication No. JP-A-2003-336731).